Intermediates for pyridoxine and process



INTERMEDIATES Fen PYRIDOXINE AND rnocnss g Peter I. Pollak, Scotch Plains, N.J., assignor to Merck & Co., Inc, Rahway, N.J., a corporation of New Jersey No Drawing. Original application Nov. 1'4, 1956, Ser. No. 621,983, now Patent No. 2,904,551, dated Sept. 15, 1959. Divided and this application Oct. 17, 1957, Ser. No. 690,635

5 Claims. (Cl. 260-295) This invention relates to processes for the production of pyridoitine (i.e., vitamin B and it is also concerned with the preparation of novel chemical compounds produced as intermediates in the synthesis of pyridoxine.

This application is a division of my copending application Serial Number 621,9 83, filed November 14, 1956, now Patent No. 2,904,551.

It is an object of this invention to provide an economical and convenient method for synthesizing pyridoxine, and to provide a series of novel intermediates.

in preparing pyridoxine I utilize as one of the startingmaterials, a derivative of pyruvic acid, which has the structural formu1a wherein X is carb-alkoxy or cyano and Y is hydroxy or cyano.

The above compound is reacted with a glycinate ester which has the formulawherein R is a lower alkyl group to form a compound of the formula- X BIC- 011100011 HO-C Patented Aug. 9, 1960 to form the straight-chain dimethyl, diethyl, dibenzyl orv diacetyl derivatives of 1,4-disubstituted butanone-2 or in which both hydroxyl groups are etherified with each other to form a cyclic inner ether, i.e., 3-keto-tetrahydrofuranel These 1,4-disubstituted butanone-Z compounds have the following structure:

cmo R e (fi- JHzOR' 0 0 wherein R is alkyl, aryl, aralkyl or acyl, to produce a pyridine derivative having the following structure:

This latter compound is acidified with dilutehydro chloric acid and heated in an autoclave at elevated temperatures to form pyridoxine hydrochloride.

The synthesis of pyridoxine and the novel intermediate, chemical compounds obtained and the process may be; illustrated by the following specific examples. It should be noted, of course, that these examples are intended tov be illustrative of the methods and procedures utilized in.

CHQO CHzCuHa CCOO C2 5 preparing these compounds and that it is not. intended to be restricted or to be regarded as embodying the only way in. which my novel chemical compounds may be formed and recovered.

Example 1 (EH 0 CHzCsHs C-CHaOOHiCtHt CHzOOOClHB 0 0"CH20 CHgCeHr I canon 116 parts of ethyl pyruvate and 103 parts of ethyl cidified with dilute hydrochloric acid. To the resulting glycinate were dissolved in anhydrous methyl alcohol consolution was added 2 parts of charcoal and the mixture taining a trace of anhydrous hydrochloric acid. After was agitated and then filtered. The filtrate as placed in standing at ambient temperature for 2 hours, the solan autoclave and the temperature maintained at 155 vent was removed by vacuum distillation and a viscous 5 C. for three hours. After vacuum dehydration, the oil of ethyl-cz-carbethoxymetl'iyliminopyruvate was reamorphous brown residue was recrystallized from hot covered. water to yield pyridoxine hydrochloride.

201 parts of the ethyl-u-carbethoxymethyliminopyruvate 197 parts of the bisulfite addition product of ethyl and 284 parts of 1,4-dibenzyloxybutanone-2 were dispyruvate, parts of sodium bisulfite, 50 parts of sodium solved in anhydrous methyl alcohol. To this solution was cyanide, and 103 parts of ethyl glycinate were dissolved. added 25 parts of anhydrous sodium carbonate and the in Water. After 8 hours standing at room temperature, mixture was agitated at 50 C. for 12 hours in a nitrogen an oily layer was separated. The aqueous layer was atmosphere. The solvent was removed by vacuum distil- 30 extracted with ether. The ether extracts were combined.

lation. The residue contained 2-methyl-3-hydroXy-4,5- with the oil and dried over sodium sulfate and distilled bis(benxyloxymethyl)-6-carbethoxy-pyridine. to yield ethyl-a-carbethoxymethylamino-a-methylcyano- The Z-methyl 3 hydroxy-4,5-bis(benzyloxymethyl)- acetate. 6-carbethoxy-pyridine thus obtained was acidified with 228 parts of ethyl-a-carbethoxymethylamino-a-methyldilute hydrochloric acid. To the resulting solution was cyanoacetate and 132 parts of 1,4-dimethoxybutanone-2 added 2 parts of charcoal and the mixture was agitated were dissolved in anhydrous pyridine to which was added and then filtered. The filtrate was placed in an auto- 5 parts of dry sodium methoxide. After 24 hours the clave and the temperature maintained at 155 C. for mixture was vacuum distilled to dryness to form a brown three hours. After vacuum dehydration, the amorphous oily residue containing 2-methyl-3-hydroxy-4,5-bis(methbrown residue was recrystallized from hot water to yield 40 oxymethyl)-6-carbethoxypyridine.

pyridoxine hydrochloride. Water was added to the brown oily residue of 2-meth- Example 2 CHzOCzHs CHzOCgH; $HOH H CHzCOOCzHs OH: H Cn0C N c-cmo 01m HO-C coH,0 0,115 HO-C CCH OH I II II H I +0 Ofl+3C2 H H3C- H, 0 H3CC\ -COOC:H5 HJC-O 0-11 0 l i N 116 .parts of ethyl pyruvate, .103 parts of ethyl glycinate yl-3-hydroxy-4,5-bis(methoxymethyl) 6 carbethoxypyrand 160 parts of 1,4-diethoxybutanone-2 were dissolved idine and charcoal was added to the aqueous suspension. in anhydrous methyl alcohol. To this solution was added The mixture was filtered. The filtrate was acidified with 20 parts of anhydrous sodium carbonate and the mixture dilute hydrochloric acid and heated in an autoclave to was agitated at 50 C. for 12 hours in a nitrogen atmos- C. for three hours. Charcoal was added to the phere. The solvent is removed by vacuum distillation reaction solution and the mixture was filtered. The filto form a residue of 2-methyl-3-hydroxy-4,5-bis(ethoxytrate was vacuum concentrated to dryness. The resultmethyl)-6-carbethoxypyridine. ing crystalline solid was recrystallized from hot water.

The crude residue of 2-methyl-3-hydroxy-4,5-bis(eth- The crystals melted at 205-206 C. and were identified oxymethyl)-6-carbethoxy pyridine thus obtained was a as pyridoxine hydrochloride.

197 parts of the \bisulfite addition product of ethyl 228 parts of ethyl-u-carbethoxymethylamino-a-methylpyruvate and 103 parts of ethyl =glycinate were dissolved cyanoacetate and 132 parts of 1,4-dimethoxybutanone2 in anhydrous diethyl ether containing 30 parts of anwere dissolved in anhydrous pyridine to which was added hydrous calcium chloride. The mixture was allowed to 5 parts of dry sodium methoxide. After twenty-four stand at room temperature for 2 hours. The mixture 5 hours at room temperature the mixture was vacuum was filtered and the solvent removed in vacuo to yield distilled to dryness. The brown oily residue contained an oily product of ethyl-u-carbethoxymethyliminopyru- 2-methyl-3-hydroxy-4,5+bis (methoxymethyl) 6 carbethvate. oxypyridine. Water was added to the 2-methyl-3-hy- 201 parts of ethyl-a-carboethoxymethyliminopymvate droxy-4,5-bis(methoxymethyl)-6-carbethoxypyridine oily thus obtained and 284 parts of 1,4-dibenzyloxybutanone.-2 10 residue and charcoal "was added to the resulting aqueous were dissolved in anhydrous methyl alcohol. To this suspension. The mixture was filtered. The filtrate was solution was added 30 parts of anhydrous sodium caracidified with dilute hydrochloric acid and heated in an inmate and the mixture was agitated at 50 C. for 12 autoclave to 155 C(tor 3 hours. Charcoal was added hours in a nitrogen atmosphere. The solvent was reto the resulting solution and the mixture is filtered. The moved by vacuum distillation to yield 2-methy1-3-hy- 15 filtrate was vacuum concentrated to dryness. The resultdroxy-4,5abis(henzyloxymethyl)-6 canbethoxypyridine. ing crystalline solid was recrystallized from hot water.

The residue of 2-methyl-3-hydroxy-4,5-bis(benzyloxy- The crystals melted at -5206 C. and were identified methyl)-6-carbethoxypyr-idine was acidified. with dilute as pyridoxine hydrochloride.

Example 6 H CHZCOOGZHE H! mom-0 N 0-0Hi0o2rn II 1130- -OH H:

SOaNa CHzOCzHs OHBOH HO-C/ o0Hi00iH5' H0C \C-CH2OH +C01+302HOH HBO-0 -c000,H5 Etc-0 H e N V N hydrochloric acid. To the resulting solution was added 197 parts of the bisulfite addition product of ethyl 2 parts of charcoal and the mixture was agitated and then pyruvate, 103 parts of ethyl glycinate and 160 parts of filtered. The filtrate was placed in an autoclave and the 1,4-diethoxybutanone-2 were dissolved in anhydrous temperature maintained at 155 C. for 3 hours. After methyl alcohol. To this solution was added 15 parts vacuum dehydration the-amorphous brown residue was of anhydrous sodium carbonate and the mixture was recrystallized from hot water to yield pyridoxine hydroagitated at 5 0 C. for 12 hours in a nitrogen atmosphere.

chloride. The solvent was removed by vacuum distillation and Example 5, p omocn,

o oH,-o0oo,m 0 CH1 ll It H|Ca- +N H8O +N ON+N HsCzO- C-CHgOCHa Bic-(i a a lit, H3C- ON GET-000cm,

CH2O on, on on HO -O' C-CHzOCHt HO-C o-omon lHCl ' 116parts of ethyl pyruvate, 120 parts of sodium bisulthe residue contained 2-methyl-3-hydroxy-4,5abis (ethoxy- 'fite,f52 parts of sodium cyanide, and 103 parts of ethyl yD- y Py "glycinate were dissolved in water. After 8 hours standing at room temperature, an oily layer was separated and the aqueous layer was extracted three times with 9 of math? ether ether F were filtrate was placed in an autoclave and the temperature bmed wlth the 011 over Sodlum sulfate and maintained at C. for three hours. After vacuum de- "disfilled to y ethybwcarbethoxymefllylamino-w-methhydration, the amorphous brown residue was recrystalylcyanoacetate. Z5 lized from hot water to yield pyridoxinehydrochloride.

bethoxy pyridine was acidified with hydrochloric acid. 70 To the resulting solution was added 2 parts of charcoal The 2 methyl-3-hydroxy-4,5-bis(ethoxymethyl) -6-carand the mixture was agitated and then filtered. The

69 parts of acetyl cyanide, 103 parts of ethyl glycinate and 188 parts of 1,4-diacetoxybutanone-2 were dissolved in anhydrous dioxane. To this solution was added 1 part of powdered sodium hydroxide and the mixture was agitated at room temperature for 24 hours. The solvent was removed by vacuum distillation to form a residue containing Z-methyl 3 amino-4,5-bis(acetoxymethyl)-6- carbethoxypyridine.

To the residue of 2-methyl-3-hydroxy-4,5-bis(acetoxymethyl)-6-carbethoxypyridine was added hydrochloric acid. 69 parts of sodium nitrite were then added at 75 C. and the resulting solution placed in an autoclave at 155 C. for three hours. After autoclaving the solution was mixed with 1 part of charcoal. The mixture was filtered and the vacuum filtrate concentrated to dryness. The residue was recrystallized from hot water to yield pyridoxine hydrochloride.

Example 8 Net H1 -6 O t z NEG C-CHrOH 69 parts of acetyl cyanide were dissolved in anhydrous pyridine and 103 parts of ethyl glycinate were added. After standing for four hours at room temperature the solvent was distilled from -the mixture to yield an oil containing wearbethoxymethylamino-propionitrile.

This oil was dissolved in anhydrous ether and 86 parts of 3-ketotetrahydrofurane was added to the mixture in the presence of trimethylbenzylammoniumhydroxide. The mixture was heated at reflux temperatures for a period of hours. The ether was removed by distillation 'to yield a residue containing 6-methyl-7-amino-4-carbethoxy l,3- dihydrofuro-[3.4-c]pyridine.'

Example 9 40 S OsNa II 1130-0 Jl-COOCaH;

CHzOH To an ether solution of 69 parts of acetyl cyanide was added 120 parts of sodium bisulfite and 52 parts of sodium cyanide. After five hours of agitation at room temperature, this mixture was filtered. The filtrate contained the bisulfite addition product of ethyl pyruvate.

To the bisulfite addition product of ethyl pyruvate filtrate was added 103 parts of ethyl glycinate and 10 parts of piperidinium acetate. This solution was refluxed on a steam bath for 12 hours. The ether was then removed by distillation and the residue contained. q:- carbethoxymethyl-amino-a-methylmalononitrile.

This residue was dissolved in anhydrous ether and 86 parts of 3-ketotetrahydrofurane was added to the mixture in the presence of trimethylbenzyl ammonium hydroxide at reflux temperature for a period of 40 hours. The'ether was removed by distillation leaving 6-methyl-7-amino 4- carbethoxy-1,3-dihydrofuro[3.4-c]pyridine.

This residue was acidified with dilute hydrochloric acid. 69 parts of sodium nitrite were then added and the mixture heated at 75 C. for three hours to form =6-methy1-7- hydroxy-4-carbethoxy-l,3-dihydrofuro[3.4-c]pyridine.

The solution was autoclaved and then charcoal was added to the mixture. The mixture was filtered and the vacuum filtrate concentrated to dryness. The residue was recrystallized from hot water to yield pyridoxine hydrochloride.

Example 10 5 +NaHSO;+NaCN- BBC-- CHa-COOCgHs NEG +N HaC-(E-CN Irh OsNB NEG +HIC0 HgG--CN onrooocim rm en,

HzC-O H|C---O Ha H2 mN-o c NaONO no-o o 1130- 6-0 0 0 02H; HaC- o-oooonn no-o o-omon +0 H OH H$G H 173 parts of the bisulfite addition product of acetyl cyanide were suspended in anhydrous pyridine and treated with 103 parts of ethyl glycinate. After four hours standing at room temperature the ether was distilled to yield an oil containing u-carbethoxymethylaminma-methylmalononitrile.

This oil was dissolved in anhydrous ether and treated with 86 parts S-ketotetrahydrofurane in the presence of trimethylbenzyl ammonium hydroxide at reflux temperatures for a period of 40 hours to form a '6-methyl-7-amino- 4-carbethoxy-l,3-dihydrofuro-[3.4-clpyridine. The ether is removed by distillation and the residue is treated in accordance with the procedure given in Example 9 to give pyridoxine hydrochloride.

Various changes and modifications may be made in carrying out the present invention without departing from the spirit and scope thereof. Insofar as these changes and modifications are within the purview of the annexed claims, they are to be considered as part of this invention.

I claim: 1. A compound of the formula:

n,c--o

HaC- b-GOOCHI wherein R is selected from the group consisting of amirid and hydroxy.

2. 6-methyl-7-amino [3.4-clpyridine.

3. 6 methyl-7-hydroxy-4-carbcthoxy-1,3 dihydrofuro [3.4-clpyridine.

4. A process that comprises reacting a derivative of pyruvic acid selected from the group consisting of compounds represented by the formula:

X HsC =0 wherein X is selected from the group consisting of carboalkoxy and cyano, with an alkali metal cyanide and a glycinate ester selected from the group consisting of compounds represented by the formula:

selected from the group of compounds represented by the formula:

- 4 carbethoxy 1,3 dihydrofuro wherein X and R have the values above assigned, reacting this compound with 3-ketotetrahydrofurane to form a pyridine derivative selected from the group consisting of compounds represented by the formula:

HgC-O Htoii 32-00012 wherein R has the value above assigned and R is selected from the group consisting of amino and hydroxy, and subjecting said compound to acid hydrolysis at elevated temperature and pressure to produce pyridoxine.

5. The process that comprises reacting acetyl cyanide, an alkali metal cyanide and ethyl glycinate to form 2- carbethoxymethylamino-a-mefihylmalononitrile, reacting the latter compound with 3-ketotetrahydrofurane to form 6 methyl-7-amino-4-carbethoxy-1,3-dihydrofuro [3.4-c] pyridine. reacting the latter compound with sodium nitrite to form 6-methyl-7-hydroxy-4-carbethoxy-1,3-dihydrofuro-[3.4-c] pyridine and subjecting the latter compound to acid hydrolysis at elevated temperature and pressure to yield pyridoxine.

References Cited in the file of this patent UNITED STATES PATENTS 2,680,743 Steven's June 8, 1954 

1. A COMPOUND OF THE FORMULA: 